Pipelines consisting of plural metal tubes which are connected with flanges, and valves provided as necessary between such metal tubes, are widely used for transporting low molecular weight organic liquids such as gasoline and fuel oil. Low molecular weight organic liquids sometimes leak from flange connections or valve portions of pipelines.
Heretofore, there has been known a sensor capable of detecting leakage of a low molecular weight organic liquid, which comprises a conductive layer showing an electric resistance variation upon contact with a low molecular weight organic liquid, formed on a core (U.S. Pat. No. 5,378,995). For use of such sensor for the detection of a low molecular weight organic liquid leakage, however, the sensor should be manufactured long enough to run adjacent to a pipeline or wind around the pipeline. When formed into, for example, a sensor of a dozen-odd meters long or longer, the maximum electric resistance of the sensor exceeds 500 k.OMEGA. to result in high impedance, since the sensor's resistance is about several dozens k.OMEGA./m (generally about 40 k.OMEGA./m). Consequently, the sensor easily suffers from external noises, so that the precise detection of electrical resistance variation upon contact with a low molecular weight organic liquid cannot be attained. For this reason, the detectable area of the above-mentioned sensor is limited to about a dozen meters long at most, which is unsuitable when the sensor should be run adjacent to the pipeline or wound therearound throughout the entire length of the pipeline.